It is well known that it is often necessary for a weak electric signal to be amplified to a corresponding strong electric signal; and, while this need arises in many fields, the present invention will be discussed primarily in terms of the needs, the problems, and some of the solutions of an "audio" system (i.e., a system for playing music for recording, for public addresses, etc.). In such systems, the weak electric signal from a musical instrument, from a microphone, from a pick-up, from a transducer, etc., is applied to an electronic "amplifier" in order to be converted to a strong electric signal; and the amplifier should be preferably small, lightweight, portable, cool-operating, noise-free, etc.
In the past, these electronic amplifiers have generally taken the form of a "linear" amplifier, the term linear amplifier amplifier indicating that the weak input signal is "linearly" amplified in such a manner that the output signal is stronger, and corresponds closely to the input signal -- i.e., is not distorted by the amplifier. Prior-art amplifiers generally took forms known as Class A, Class B, Class AB, Class C, Push-Pull, and the like, specific amplifier configurations being selected because of the desired input, output, required conditions of operation, or desired results. Unfortunately, such amplifiers (and their associated "power supplies") have the disadvantage that they are relatively inefficient, their inefficiencies producing heating effects. These, in turn, required cooling facilities, such as fans -- the fans introducing an additional disadvantage, in that they required additional power, and produced spurious effects such as noises and vibrations that found their way into the electric or audible output. These spurious effects are intolerable in high-quality systems, or in locations such as recording studios. Moreover, the prior-art amplifiers and power supplies usually operated in the 60 Hertz range; and their circuitry required relatively large, bulky, and heavy electronic components -- these reducing portability.